Estudo da evolução das cabeceiras de drenagem como subsídio para o entendimento da morfodinâmica de divisor de drenagem das bacias hidrográficas dos rios Moxotó e Capiá – AL/PE.

Abstract

The drainage dividers are important limits of organization for landscapes; the dynamics belonging to these elements have an intrinsic relationship with the drainage headwaters and their advance over the dividers. These dynamics are associated with several variables, such as the distribution of rocky substrates of different strengths and the climatic variations, they are important elements for understanding the dynamics belonging to the objects of study of this work. Thus, this work aims at a morphometric analysis on a geomorphological basis, the drainage divisor, located between two hydrographic basins located in the states of Alagoas and Pernambuco (Moxotó and Capiá River basins), as well as the drainage headwaters that connect with the divisor. For this, a series of parameters and indexes of quantitative nature were applied either to the divider, or to the drainage headwaters, in order to enable the morphometric analysis. This began with the drainage network hierarchization according to Strahler (1952), serving to delimit the 2nd order basin areas. Using the Topotoolbox function set and the Topographic analysis kit in the Matlab environment, other indexes directly applied to the drainage network were calculated, such as the χ and Ksn value indexes; the analysis of the drainage basins also included the elaboration of hypsometric curves and the application of the drainage basin asymmetry factor. The structural analysis was done by extracting the relief lineaments for the analyzed area for four illumination angles (45°, 90°, 315° and 360°) in order to characterize the direction of the main structures acting in the relief organization, in order to influence the dynamics belonging to the headwater-divider relations. Finally, the divider asymmetry index (DAI), and its preferential migration direction were calculated. In this way it was possible to establish relationships between the dynamics of migration and headland advance with the main structures operating in the area.